N-acetylcysteine compositions and methods for the treatment and prevention of drug toxicity

ABSTRACT

The invention provides pharmaceutical compositions for the treatment or prevention of the toxic effects of therapeutic agents and methods of treating or preventing such toxicity using a toxicity reducing amount of N-acetylcysteine either alone or in combination with a therapeutically effective amount or, to achieve its therapeutic advantages, an amount larger than what is customarily given as a therapeutically effective amount, of a therapeutic agent. The invention also provides pharmaceutical compositions for the treatment or prevention of the toxic effects of therapeutic agents and methods of treating or preventing such toxicity using a toxicity reducing amount of N-acetylcysteine either alone or in combination with a therapeutically effective amount or, to achieve its therapeutic advantages, an amount larger than what is customarily given as a therapeutically effective amount, of a therapeutic agent whose side effects are made worse by increased oxidative stress or treatment related decreases in subject cysteine/glutathione levels or are otherwise relieved by administration of NAC.

GOVERNMENT SUPPORT

[0001] This work is supported at least in part by grants from the N.I.H.CA42509-14. The government may have certain rights in this invention.

FIELD OF THE INVENTION

[0002] The present invention relates to compositions for the treatmentor prevention of drug toxicity in mammals including humans which mayresult from the administration of therapeutic agents and to methods oftreating or preventing such toxicity. The compositions of this inventioncomprise a toxicity-reducing amount of N-acetylcysteine (NAC) alone orin combination with a therapeutically effective amount or, to achieveits therapeutic advantages, an amount larger than what is customarilygiven as a therapeutically effective amount, of a therapeutic agent,preferably in combination with a pharmaceutically acceptable carrier.The method of treating or preventing drug toxicity in humans comprisesadministering a toxicity-reducing amount of NAC alone or in combinationwith a therapeutically effective amount or, to achieve its therapeuticadvantages, an amount larger than what is customarily given as atherapeutically effective amount, of a therapeutic agent, preferably incombination with a pharmaceutically acceptable carrier.

BACKGROUND OF THE INVENTION

[0003] Glutathione (GSH), a tripeptide that is normally found in allanimal cells and most plants and bacteria at relatively high (1-10millimolar) concentrations, helps to protect cells against oxidativedamage that would otherwise be caused by free radicals and reactiveoxidative intermediates (ROIs) produced during cell metabolism or as theresults of, for example, drug overdose. Glutathione is itself the majorscavenger of reactive oxidative intermediates present in all eukaryoticforms of life and is generally required to protect cells against damageby oxidants. Glutathione reduces (and thereby detoxifies) intracellularoxidants and is consumed by this reaction. Glutathione is oxidized tothe disulfide linked dimer (GSSG), which is actively pumped out of cellsand becomes largely unavailable for reconversion to reduced glutathione.Thus, unless glutathione is resynthesized through other pathways,utilization of this compound is associated with a reduction in theamount of glutathione available. The antioxidant effects of glutathioneare also mediated less directly by the role of this compound inmaintaining other antioxidants in reduced form. Thus, pharmaceuticalcompounds that replenish or elevate glutathione levels work, at least inpart, through enhancement of the defense mechanisms seemingly utilizedto normally protect tissue from ROI mediated damage.

[0004] Glutathione depletion has been implicated in the pathology of anumber of diseases including infection by human immunodeficiency virus(HIV). In HIV infection, cysteine/glutathione depletion is known toimpair T-cell function and is associated with impaired survival ofsubjects with less than 200 CD4 T-cells per μl blood.

[0005] Drug toxicity is a very widespread problem. Cysteine/glutathionedepletion and oxidative stress (See U.S. Pat. No. 4,757,063) intensifydrug toxicity effects and have been implicated in the mechanism of drugtoxicity reactions.

[0006] For example, acetaminophen is known to act to depletecysteine/glutathione and cause a variety of drug toxicity symptoms.Acetaminophen, also known as paracetamol and N-acetyl-p-aminophenol, isone of the most widely used pharmaceutical analgesic and antipyreticagents in the world. It is contained in over 100 products and iscommonly found in the U.S. as immediate release tablets and asextended-release preparations. Various children's chewable, suspension,and elixir formulations that contain acetaminophen are prevalent.Acetaminophen is also found as a component of combination drugs, such aspropoxyphene/acetaminophen and oxycodone/acetaminophen.

[0007] Acetaminophen continues to be the most commonly encounteredsubstance in toxic ingestions. In many cases, acetaminophen overdosesare unintentional and are undiagnosed until after substantial damage hasalready occurred. Repeated administration of acceptable size doses ofacetaminophen can produce toxicity symptoms. As discussed by Donovan(1999) Academic Emergency Med. 6:1079-1082, methods for detectingpost-ingestion blood levels of acetaminophen suffer from poor predictivevalues. Even in the simple case of a single acute ingestion, patientswith no discernible risk factors for liver injury and low blood levelsof acetaminophen still develop toxicity and even die.

[0008] Many companies package acetaminophen under different trade names,resulting in inadvertent overdosing by less sophisticated patients andparents who do not read the information on the packaging. In addition,cold remedies and other over-the-counter preparations often containacetaminophen, which is listed among a series of generic drug names thatare difficult for patients and parents to read. Therefore, patientsoften are unaware of the amount of acetaminophen that they havereceived. Children are especially vulnerable to accidental exposure dueto their smaller size, the presence of acetaminophen in multipleover-the-counter remedies, and a reluctance to administer aspirin andother NSAIDs to children for fever due to the risk of Reye's Syndromeand renal tubular injury. The antipyretic value of acetaminophen clearlyhas been demonstrated and hence acetaminophen is widely used inhospitals for this purpose. However, acetaminophen may not be theantipyretic agent of choice under circumstances where renal or hepaticfunction is in danger of being compromised.

[0009] It is well established that large acetaminophen overdose causeshepatotoxicity and, in some cases, nephrotoxicity in humans and inexperimental animals. Acute overdosage of acetaminophen results indose-dependent and potentially fatal hepatic necrosis as well as (inrare cases) renal tubular necrosis and hypoglycemia. Acetaminophen israpidly absorbed from the stomach and small intestine and is normallymetabolized by conjugation in the liver to nontoxic agents, which arethen eliminated in the urine. In acute overdoses, or when maximum dailydoses are exceeded over a prolonged period, the normal pathways ofmetabolism become saturated.

[0010] Excess acetaminophen is metabolized in the liver via the mixedfunction oxidase P450 system to a toxic, N-acetyl-p-benzoquinone-Imine(NAPQI). NAPQI has an extremely short half-life and is rapidlyconjugated with glutathione, a sulfhydryl donor, and removed from thesystem. Under conditions of excessive NAPQI formation or reducedglutathione stores, NAPQI is free to bind to vital proteins and thelipid bilayer of hepatocytes. This results in hepatocellular death andsubsequent centrilobular liver necrosis. Immumunohistochemical studieshave suggested that NAPQI-protein adducts appear even at sub-hepatotoxicacetaminophen doses and before depletion of total hepatic glutathionewhich may be related to rare cases of hypersensitivity. In addition,decreased intracellular cysteine/glutathione can contribute to celldeath via mechanisms that do not involve NAPQI.

[0011] The direct cost of acetaminophen overdose has been estimated tobe $87 million annually. Effective protocols have been developed andtested to stratify risk and treat patients who present soon after asingle large dose of acetaminophen. However, many patients present aftera delay long enough to metabolize all the acetaminophen, after two ormore ingestions over several hours, or after several days of excessiveself-medication. Under these circumstances it is difficult for theclinician to estimate the risk of adverse outcome before hepatic orrenal injury occurs. See, for example, Bond and Hite (1999) Acad. Emerg.Med. 6:1115-1120; and Donovan (1999) Acad. Emerg. Med. 6:1079-1082.However, early treatment of acetaminophen overdosage is considered to becrucial, and vigorous supportive therapy is essential when intoxicationis severe.

[0012] Nucleoside reverse transcriptase inhibitors (NRTIs), of which thepyrimidine nucleoside analogue azidothymidine (AZT, zidovudine), is acommon example, are often given in combination therapies with otheranti-retroviral drugs to treat HIV. Long-term therapy with AZT iscommonly associated with dose-dependent hematologic toxicity whichmanifests as low erythrocyte counts and elevated mean red cell volume,and with muscle fiber toxicity, particularly in patients with advancedHIV disease. Some studies indicate that AZT's toxic interactions resultfrom the generation of reactive oxygen species (ROIs) that react withand deplete intracellular glutathione levels. See de la Asuncion, et al(1998) J. Clin. Invest. 102(1): 4-9; Gogu et al. (1991) Exp. Hematol.19(7): 649-652; Gogu and Agrawal (1996) Life Sci. 59 (16): 1323-1329;Prakash et al (1997) Arch. Biochem. Biophys. 343 (2): 173-80.

[0013] Results have shown that acetaminophen usage, which lowersglutathione levels exacerbates AZT toxicity. Richman, et al. (1987) N.Eng. J. Med. 317: 192-97. De Rosa et al. recently have shown thattreatment with NAC which increases glutathione levels decreases thetoxicity. De Rosa et al., submitted to JAMA for publication.

[0014] Evidence from in vitro and animal studies supports thisconclusion. AZT treatment caused oxidative damage to mitochondrial DNA(including increased mitochondrial lipoperoxidation) and increasedlevels of oxidized glutathione in skeletal muscle in mice. See de laAsuncion, et al. (1998) J. Clin. Invest. 102(1): 4-9. NAC and theanti-oxidant Vitamins C and E have been shown to prevent thisAZT-induced toxicity. See id.; Gogu, et al (1991) Exp. Hematol. 19,649-52; and Gogu and Agrawal (1996) Life Chem. Rep. 4, 1-35.Furthermore, AZT treatment intensifies glutathione depletion in HIV-TATtransgenic mice (see Prakash, O., et al. Arch. Biochem. Biophys. (1997)343: 173-80) where expression of the TAT protein has been shown todeplete glutathione by decreasing glutathione biosynthesis (see Choi,J., et al., (2000) J. Biol. Chem. 275 (5): 3693-98) and the activity ofantioxidant enzymes (Flores et al. (1993) Proc. Nat. Acad. Sci. 90 (16):7632-36). Studies with TAT-transgenic mice also show that AZT toxicityis enhanced in this glutathione-depleted environment. See Prakash et al.(1997) Arch. Biochem. Biophys. 343, 173-80.

[0015] Early clinical trials of AZT efficacy in HIV disease revealed anassociation between AZT toxicity and the use of acetaminophen. See,e.g., Richman, et al. (1987) New Eng. J. Med. 317(4): 192-97. Althoughthe mechanism of this toxic reaction is not fully understood,acetaminophen does not impair AZT detoxification since no difference inAZT's rate of destruction has been observed. Since acetaminophen isknown to deplete glutathione, the potentially harmful effect ofco-administering acetaminophen and AZT appears to be mediated throughglutathione depletion. Thus, in conditions where glutathione already isdepleted, such as in later stages of HIV disease, detoxification ofacetaminophen (which can be expected to further deplete glutathionestores in the liver and elsewhere) would increase the potential for AZTtoxicity.

[0016] Long-term antibiotic usage also often produces drug toxicityreactions. Toxicity reactions for a given antibiotic are a function ofits mechanism of action and the pathway(s) by which it is metabolicallydegraded.

[0017] Scientists have long sought to identify agents that will begenerally effective in combating drug toxicity reactions. Protectiveagents for drug overdose have been extensively studied. A known methodof treatment for acetaminophen overdose is the administration ofsulfhydryl compounds. L-methionine, L-cysteine, and either the purifiedL-enantiomer or the racemate mixture of N-acetylcysteine are known tohave a protective action in animals. Methionine and another sulfhydrylcompound, cysteamine, have been reported to provide some protection.Also, cimetidine, dimethyl sulfoxide, and ethanol have been shown toinhibit acetaminophen bioactivation. N-acetylcysteine has been shown tobe effective in humans when given orally. Early administration ofcompounds supplying sulfhydryl groups (0 to 10 hours after acetaminopheningestion) may prevent or minimize hepatic and renal injury in cases ofacetaminophen overdose. NAC is now used by many physicians for treatmentof hepatic failure of any etiology, whether known or unknown, and is theaccepted antidote for cyclophosphamide poisoning. NAC also is used toprevent toxicity due to radiation therapy contrast material in patientsundergoing such treatment. The mechanisms through which NAC prevents orreverses toxicity are mainly thought to involve glutathionereplenishment. However, additional mechanisms through which NAC worksdirectly via the cysteine molecule itself are not excluded.

[0018] Recently we have shown that treatment with NAC decreases AZT'shematologic toxicity in subjects taking AZT. It appears that NACprovides cysteine needed to redress the excessive sulfur loss thatoccurs in HIV disease and specifically to replenish intracellularglutathione. This in turn helps to restore the reducing power necessaryfor deoxynucleotide synthesis and to bring the size of thedeoxynucleotide pool, and hence the rate of cell division, back intonormal range. This decreases the AZT-mediated inhibition of erythroiddevelopment, helps to improve the overall metabolism and stability oferythrocytes and their progenitors (for example, by enabling optimalfunctioning of the glucose-6-phosphate dehydrogenase and otherenergy-supplying pathways). In addition, it improves the cell's abilityto withstand the production of oxidants induced by the introduction ofdrugs (such as AZT) and the internal production of molecules (such asTNF and HIV-TAT) that trigger intracellular oxidant production.

[0019] Improved formulations and methods to prevent drug toxicityreactions during long term therapy are of particular interest in view ofthe considerable loss of life attributable to, and cost of treatment of,such reactions. The present invention addresses this problem.

SUMMARY OF THE INVENTION

[0020] Pharmaceutical compositions and methods of treatment are providedfor serial or co-administration of NAC with any therapeutic agent todecrease drug toxicity, including those drugs whose side effects aremade worse by decreases in subject intracellular cysteine/gluathionelevels or increased oxidative stress, or whose side effects areotherwise relieved by administration of NAC. The serial orco-administration of NAC makes a therapeutic agent safer at currentlyrecognized standard therapeutic doses and allows increased doses of thattherapeutic agent to be administered for its beneficial purposes withouttoxic side effects.

[0021] According to one embodiment of the invention, compositions usefulfor treating or preventing the toxic effects of therapeutic agents inmammals are provided comprising a toxicity-reducing amount ofN-acetylcysteine or a pharmaceutically acceptable salt or derivativethereof alone or in combination with a therapeutic or greater amount ofa therapeutic agent, in combination with a pharmaceutically acceptableexcipient or carrier. In another embodiment, such compositions compriseat least about 1 mg N-acetylcysteine or a pharmaceutically-acceptablesalt or derivative thereof. In another embodiment, such compositionscomprise a therapeutic amount of a therapeutic agent in combination witha toxicity-reducing amount of NAC or a pharmaceutically acceptable saltor derivative thereof, wherein the therapeutic agent is at least oneantibiotic or antiviral agent. In another embodiment, such compositionscomprise a therapeutic amount of a therapeutic agent in combination witha toxicity-reducing amount of NAC or a pharmaceutically acceptable saltor derivative thereof, wherein the therapeutic agent is at least oneantibiotic or antiviral agent that produces oxidative stress. In anotherembodiment, such compositions comprise a therapeutic amount of atherapeutic agent in combination with a toxicity-reducing amount of NACor a pharmaceutically acceptable salt or derivative thereof, wherein thetherapeutic agent is at least one antibiotic or antiviral agent thatproduces treatment-related decreases in subject cysteine/glutathionelevels. In another embodiment, such compositions comprise a therapeuticamount of a therapeutic agent in combination with a toxicity-reducingamount of NAC or a pharmaceutically acceptable salt or derivativethereof, wherein the therapeutic agent is an analgesic, antipyretic orother therapeutic compound. In another embodiment, such compositionscomprise a therapeutic amount of a therapeutic agent in combination witha toxicity-reducing amount of NAC or a pharmaceutically acceptable saltor derivative thereof, wherein the therapeutic agent is an analgesic,antipyretic or other therapeutic compound that produces oxidativestress. In another embodiment, such compositions comprise a therapeuticamount of a therapeutic agent in combination with a toxicity-reducingamount of NAC or a pharmaceutically acceptable salt or derivativethereof, wherein the therapeutic agent is an analgesic, antipyretic orother therapeutic compound that produces treatment-related decreases insubject cysteine/glutathione levels. In another embodiment, suchcompositions comprise a therapeutic amount of a therapeutic agent incombination with a toxicity-reducing amount of NAC or a pharmaceuticallyacceptable salt or derivative thereof, wherein the compound is aparaminophenol derivative, which includes phenacetin and its activemetabolite acetaminophen. In another embodiment, such compositionscomprise a therapeutic amount of a therapeutic agent in combination witha toxicity-reducing amount of NAC or a pharmaceutically acceptable saltor derivative thereof, wherein each dosage unit contains a standard doseof acetaminophen and at least about 1 mg of NAC. In another embodiment,such compositions comprise a therapeutic amount of a therapeutic agentin combination with a toxicity-reducing amount of NAC or apharmaceutically acceptable salt or derivative thereof, wherein thetherapeutic agent is an anti-retroviral agent. In another embodiment,such compositions comprise a therapeutically effective amount of AZT incombination with a toxicity-reducing amount of NAC to decrease keyaspects of AZT toxicity in human HIV patients, e.g., macrocytic anemia.

[0022] In another embodiment, a method of treating or preventing thetoxic effects of therapeutic agents in mammals comprises administering atoxicity reducing amount of NAC or a pharmaceutically acceptable salt orderivative thereof, alone or in combination with a normal dosage or agreater than normal dosage of a therapeutic agent, in combination with apharmaceutically acceptable carrier. In another embodiment, the methodcomprises administering at least about 1 mg NAC or a pharmaceuticallyacceptable salt or derivative thereof to a patient receiving nutritionparenterally. In another embodiment, the method comprises administeringa therapeutic amount of at least one antibiotic or antiviral agent incombination with NAC or a pharmaceutically acceptable salt or derivativethereof. In another embodiment, the method comprises administering atherapeutic amount of at least one antibiotic or antiviral agent incombination with NAC or a pharmaceutically acceptable salt or derivativethereof wherein the antibiotic or antiviral agent produces oxidativestress. In another embodiment, the method comprises administering atherapeutic amount of at least one antibiotic or antiviral agent incombination with a toxicity-reducing amount of NAC or a pharmaceuticallyacceptable salt or derivative thereof, wherein the antibiotic orantiviral agent produces treatment-related decreases in subjectcysteine/glutathione levels. In another embodiment, the method comprisesadministering a therapeutic amount of an anti-retroviral agent incombination with a toxicity reducing amount of NAC. In anotherembodiment, the method comprises administering a therapeutic amount ofan anti-retroviral agent in combination with a toxicity-reducing amountof NAC wherein the anti-retroviral agent is AZT. In another embodiment,the method comprises administering a therapeutic amount of AZT seriallyor in combination with a toxicity-reducing amount of NAC perinatally. Inanother embodiment, the method comprises administering a therapeuticamount of AZT serially or in combination with a toxicity-reducing amountof NAC neonatally. In another embodiment, the method comprisesadministering a therapeutic amount of AZT for suspected or knownexposure to the HIV virus serially or in combination with atoxicity-reducing amount of NAC. In another embodiment, the methodcomprises administering a therapeutic amount of at least one analgesic,antipyretic or other therapeutic compound in combination with a toxicityreducing amount of NAC or a pharmaceutically acceptable salt orderivative thereof. In another embodiment, the method comprisesadministering a therapeutic amount of at least one analgesic,antipyretic or other therapeutic compound in combination with atoxicity-reducing amount of NAC, wherein the compound produces oxidativestress. In another embodiment, the method comprises administering atherapeutic amount of at least one analgesic, antipyretic or othertherapeutic compound in combination with a toxicity-reducing amount ofNAC, wherein the compound produces treatment-related decreases insubject cysteine/glutathione levels. In another embodiment, the methodcomprises administering a therapeutic amount of at least one analgesic,antipyretic or other therapeutic compound in combination with atoxicity-reducing amount of NAC wherein the compound is a paraminophenolderivative, which includes phenacetin and its active metaboliteacetaminophen. In another embodiment, the method comprises administeringa therapeutic amount of acetaminophen in a standard dosage serially orin combination with at least about 1 mg per dose N-acetylcysteine totreat a fever or pain in a patient who responds normally toacetaminophen. In another embodiment, the method comprises administeringa greater than standard dosage of acetaminophen serially or incombination with at least about 4 mg/kg N-acetylcysteine to treat afever nonresponsive to the standard dose of acetaminophen. In anotherembodiment, the method comprises administering a standard dosage ofacetaminophen serially or in combination with at least about 1 mg perdose N-acetylcysteine to treat patients who require acetaminophen duringtheir exposure to radiation contrast agents.

[0023] The combined compositions and methods provide protection againsttoxic drug reactions, particularly where overdosing may be inadvertent,undiagnosable, or even therapeutically desirable if the toxic sideeffects could be removed.

DETAILED DESCRIPTION OF THE INVENTION

[0024] The invention described herein provides for the serial orco-administration of any therapeutically active agent with NAC torelieve the toxic effects of such therapy in mammals including wheretoxic effects of such therapy in mammals may be due to oxidative stressor treatment-related decreases in subject cysteine/glutathione levels orare otherwise relieved by administration of NAC.

[0025] The pharmaceutical compositions and methods of treatment abovedescribed include providing the pharmaceutical compositions in oral,parenteral or suppository form for oral, parenteral or rectaladministration. It is preferred that the NAC be substantially free ofsulfones or other chemicals that interfere with the metabolism of theco-administered drug, e.g., acetaminophen, in its bioactive form. It isalso preferred that the NAC be substantially free of its oxidized form,di-n-acetylcysteine. It is preferred that the therapeutic agent,serially or co-administered, be in any form in which it is typicallyavailable and the composition should be prepared in a manner thatsubstantially prevents oxidation of the NAC during preparation orstorage.

[0026] In one aspect of the invention, the combined formulation isadministered to individuals having an increased susceptibility foracetaminophen toxicity. With regard to acetaminophen toxicity in adults,hepatotoxicity may occur after ingestion of a single dose of more thanabout 7.5 to 10 g of acetaminophen. However, alcoholics and individualstaking isoniazid have elevated P-450 2E1 levels and can have increasedsusceptibility for acetaminophen toxicity. The risk of hepatotoxicitywith single or serial doses of acetaminophen may also be increased inpatients regularly taking other hepatic enzyme-inducing agents,especially barbiturates or other anticonvulsants. In addition,individuals taking classes of antibiotics that reduce GSH, includingsulfas, chloramphenicol, macrolides and fluoroquinolones, may haveincreased risk of hepatotoxicity with acetaminophen. Also, although mostacetaminophen is metabolized through the glucoronidation pathway inadults, some is converted to a reactive intermediate that is detoxifiedin a GSH-dependent reaction. See Thomas, S. H. (1993) Pharmacol. Ther.60: 91-120. Pre-adolescent children, particularly below school age, lackthe normal glucoronidation pathway and rely to a greater degree thanadults on GSH for detoxification of acetaminophen, increasing theirsusceptibility to acetaminophen-induced-toxicity. Further, patientsreceiving parenteral nutrition who may not receive an adequate dietarysource of cysteine or whose condition may result in oxidative stresswill have an increased susceptibility to acetaminophen toxicity.Increased susceptibility can also result from a predisposition to GSHdeficiency, due to HIV and other infections, metabolic diseases, e.g.,diabetes, chronic diseases, sepsis, hepatic insufficiency and otherphysiologic oxidative stress.

[0027] With respect to acetaminophen, the formulations of the presentinvention find use as anti-pyretic and analgesic agents, and aresuitable for medical indications treatable with acetaminophen alone. Animprovement in product safety is provided by the inclusion of NAC, whichsubstantially prevents the possibility of accidental or inadvertentoverdosage. The combined use of acetaminophen and NAC enhances thedesired effects of acetaminophen while preventing its side effects, e.g.administering acetaminophen with NAC can allow acetaminophen dosing athigher levels, which would otherwise carry an unacceptable risk oftoxicity. The co-formulation with NAC can enhance the safety ofacetaminophen administration in severe illness and hence decreasepatient morbidity and mortality due to acetaminophen-induced hepatic andrenal injury. NAC administration may provide an additional benefit sinceit tends to reduce the negative effects of tumor necrosis factor alpha(TNF-α) and similar-acting cytokines.

[0028] NAC replenishes glutathione following acetaminophen overdose,which otherwise leads to a fatal depletion of glutathione in the liver.This non-toxic drug enters cells readily and replenishes theintracellular cysteine required to produce glutathione, thus leading toan increase in glutathione levels. It is important to note that NAC doesnot interfere with the peripheral action of acetaminophen as ananalgesic or anti-pyretic, and thus its presence in the combinedformulations of the invention does not decrease the potency of thetherapeutic agent. It may be noted that the effectiveness of NAC dependson the presence of the reduced form, which may, for example, liberatethe reduced form of glutathione from homo- and hetero-disulfidederivatives in thiol-disulfide exchange reactions. The unit dose ofacetaminophen in the provided formulation may be higher than theconventional dose in the absence of NAC. A typical unit dosage may be asolution suitable for oral or intravenous administration; aneffervescent tablet suitable for dissolving in water, fruit juice, orcarbonated beverage and administered orally; a tablet taken from two tosix times daily, or one time-release capsule or tablet taken once ortwice a day and containing a proportionally higher content of activeingredient, etc. The time-release effect may be obtained by capsulematerials that dissolve at different pH values, by capsules that releaseslowly by osmotic pressure, or by any other known means of controlledrelease. Unit dosage forms may be provided wherein each dosage unit, forexample, teaspoonful, tablespoonful, gel capsule, tablet or suppository,contains a predetermined amount of the compositions of the presentinvention. Similarly, unit dosage forms for injection or intravenousadministration may comprise the compound of the present invention in acomposition as a solution in sterile water, normal saline or anotherpharmaceutically acceptable carrier. The specifications for the unitdosage forms of the present invention depend on the effect to beachieved and the intended recipient.

[0029] It is preferred that the pharmaceutical compositions according tothe present invention contained from about 80 mg to about 2000 mg ofacetaminophen per dosage unit, particularly from about 650 mg to about2000 mg per dosage unit. The amount of NAC per dosage unit is preferablyfrom 1 mg to 25000 mg, preferably at least 3 mg to 2,000 mg per dosageunit for oral administration, and 20-20,000 mg for parenteral.

[0030] The acetaminophen present in orally administrable solid unitdoses will usually be at least about 80 mg (for pediatric doses), 325mg, 500 mg and 650 mg, and may be as high as about 2000 mg, more usuallynot more than about 1500 mg together with effective amounts of NAC.Suppositories are formulated in the manner well known in the art andusually comprise at least about 120 mg, 125 mg, 325 mg, 500 mg and 650mg acetaminophen per dosage unit and may be as high as about 2000 mg,more usually not more than about 1500 mg together with effective amountsof NAC. Oral liquid dosage forms usually comprise at least about 100mg/ml, 120 mg/2.5 ml, 120mg/5 ml, 160 mg/5 ml, 165 mg/5 ml, 325 mg/5 mlacetaminophen, and may be as high as about 2000 mg, more usually notmore than about 1500 mg together with effective amounts of NAC.

[0031] The unit dose of NAC, in combination with any one of the abovedoses of acetaminophen, or alone for the treatment of acute hepaticinjury in the absence of toxic levels of acetaminophen, will usuallycomprise at least about 1.5 mg/kg to a maximum amount of 70 mg/kg (forpediatric doses), usually at least about 500 mg (for adult doses); andusually not more than about 2,000 mg at the physician's discretion.Patients on therapy known to deplete cysteine/glutathione or produceoxidative stress may benefit from higher amounts of NAC.

[0032] Over-the-counter NAC can be variably produced and packaged.Because the production and packaging methods generally do not guardagainst oxidation, the NAC can be significantly contaminated withbioactive oxidation products. These may be particularly important inview of data indicating that the oxidized form of NAC has effectscounter to those reported for NAC and is bioactive at doses roughly10-100 fold less than NAC (see Samstrand et al (1999) J. Pharmacol. Exp.Ther. 288: 1174-84).

[0033] The distribution of the oxidation states of NAC as a thiol anddisulfide depends on the oxidation/reduction potential. The half-cellpotential obtained for the NAC thiol/disulfide pair is about +63 mV,indicative of its strong reducing activity among natural compounds (seeNoszal et al. (2000) J. Med. Chem. 43:2176-2182). In a preferredembodiment of the invention, the preparation and storage of theformulation is performed in such a way that the reduced form of NAC isthe primary form administered to the patient. Maintaining NAC containingformulations in solid form is preferable for this purpose. When insolution, NAC containing formulations are preferably stored in a brownbottle that is vacuum sealed. Storage in cool dark environments is alsopreferred.

[0034] The determination of reduced and oxidized species present in asample may be determined by various methods known in the art, forexample with capillary electrophoresis, HPLC, etc. as described byChassaing et al. (1999) J Chromatogr B Biomed Sci Appl 735(2):219-27.

[0035] The compositions of the present invention may be administeredorally, parenterally, or rectally in dosage unit formulations containingconventional nontoxic pharmaceutically acceptable carriers, adjuvants,and vehicles as desired. The term parenteral as used herein includessubcutaneous injections, intravenous, intramuscular, intrasternalinjection, or infusion techniques. Topical administration may alsoinvolve the use of transdermal administration such as transdermalpatches or iontophoresis devices which are prepared according totechniques and procedures well known in the art.

[0036] Solid dosage forms for oral administration may include capsules,tablets, pills, powders, granules and gels. In such solid dosage forms,the active compounds may be admixed with at least one inert diluent suchas sucrose, lactose or starch. Such dosage forms may also comprise, asin normal practice, additional substances other than inert diluents,e.g., lubricating agents such as magnesium stearate. In the case ofcapsules, tablets, and pills, the dosage forms may also comprisebuffering agents. Tablets and pills can additionally be prepared withenteric coatings.

[0037] Suppositories for rectal administration of the drug composition,such as for treating pediatric fever etc., can be prepared by mixing thedrug with a suitable nonirritating excipient such as cocoa butter andpolyethylene glycols which are solid at ordinary temperatures but liquidat the rectal temperature and will therefore melt in the rectum andrelease the drug.

[0038] Injectable preparations, for example, sterile injectable aqueousor oleaginous suspensions, may be formulated according to the known artusing suitable dispersing or wetting agents and suspending agents. Thesterile injectable preparation may also be a sterile injectable solutionor suspension in a nontoxic parenterally acceptable diluent or solvent,for example, as a solution in 1, 3-butanediol. Among the acceptablevehicles and solvents that may be employed are water, Ringer's solution,and isotonic sodium chloride solution. In addition, sterile, fixed oilsare conventionally employed as a solvent or suspending medium.

[0039] The compositions of this invention can further includeconventional excipients, i.e., pharmaceutically acceptable organic orinorganic carrier substances suitable for parenteral application whichdo not deleteriously react with the active compounds. Suitablepharmaceutically acceptable carriers include, but are not limited to,water, salt solutions, alcohol, vegetable oils, polyethylene glycols,gelatin, lactose, amylose, magnesium stearate, talc, silicic acid,viscous paraffin, perfume oil; fatty acid monoglycerides anddiglycerides, petroethral fatty acid esters, hydroxymethylcellulose,polyvinylpyrrolidone, etc. The pharmaceutical preparations can besterilized and if desired, mixed with auxiliary agents, e.g.,lubricants, preservatives, stabilizers, wetting agents, emulsifiers,salts for influencing osmotic pressure, buffers, colorings, flavoringand/or aromatic substances and the like which do not deleteriously reactwith the active compounds. For parenteral application, particularlysuitable vehicles consist of solutions, preferably oily or aqueoussolutions, as well as suspensions, emulsions, or implants. Aqueoussuspensions may contain substances which increase the viscosity of thesuspension and include, for example, sodium carboxymethyl cellulose,sorbitol and/or dextran. Optionally, the suspension may also containstabilizers.

[0040] The composition, if desired, can also contain minor amounts ofwetting or emulsifying agents or pH buffering agents. The compositioncan be a liquid solution, suspension, emulsion, tablet, pill, capsule,sustained release formulation, or powder. The composition can beformulated as a suppository, with traditional binders and carriers suchas triglycerides. Oral formulations can include standard carriers suchas pharmaceutical grades of mannitol, lactose, starch, magnesiumstearate, sodium saccharine, cellulose, magnesium carbonate, etc.

[0041] The therapeutically active agent of the present invention can beformulated per se or in salt form. Pharmaceutically acceptable saltsinclude, but are not limited to, those formed with free amino groupssuch as those derived from hydrochloric, phosphoric, sulfuric, acetic,oxalic, tartaric acids, etc., and those formed with free carboxyl groupssuch as those derived from sodium, potassium, ammonium, calcium, ferrichydroxides, isopropylamine, triethylamine, 2-ethylamino ethanol,histidine, procaine, etc.

[0042] The amount of compounds in the compositions of the presentinvention which will be effective in the treatment of a particulardisorder or condition will depend on the nature of the disorder orcondition, and can be determined by standard clinical techniques. See,for example, Goodman and Gilman; The Physician's Desk Reference, MedicalEconomics Company, Inc., Oradell, N. J., 1995; and to Drug Facts andComparisons, Facts and Comparisons, Inc., St. Louis, Mo., 1993. As theaddition of NAC does not affect the therapeutic efficacy ofacetaminophen, it is generally not necessary to adjust the dosage fromwhat would ordinarily be administered for acetaminophen alone, and infact the dose may be raised due to the increased safety of the presentformulations. The precise dose to be employed in the formulation willalso depend on the route of administration, and the seriousness of thedisease or disorder, and should be decided according to the judgment ofthe practitioner and each patient's circumstances.

[0043] The present invention also provides a pharmaceutical pack or kitcomprising one or more containers filled with one or more of theingredients of the pharmaceutical compositions of the invention.Associated with such container(s) can be a notice in the form prescribedby a governmental agency regulating the manufacture, use or sale ofpharmaceuticals or biological products, which notice reflects approvalby the agency of manufacture, use or sale for human administration.

[0044] In another embodiment of the invention, formulations of NAC areprovided for the treatment of acute hepatic failure of unknown etiology,for example for the treatment of acetaminophen or other drug toxicitywhere the serum levels of the toxic drug indicate non-toxic levels wherethere may be an increased risk for toxicity due to oxidative stress orother aspects of the patient's condition. The NAC formulations fortreatment of such patients will utilize a formulation as describedabove.

[0045] Many such patients having severe hepatic failure also have serumlevels of acetaminophen within the accepted non-toxic range, due tovarious factors. Such factors may include the lapsed time beforepresentation of the toxic effects, for example in incidences ofintentional overdose.

[0046] Inadvertent acetaminophen toxicity has also been reported withnormally accepted dosing regimens when associated with certain viralinfections, toxic exposure, and drug use, such as sulfa, chloramphenicoland erythromycin. Many of these patients present with non-toxicacetaminophen levels, but toxicity still results from oxidative stressand other drug-related effects on hepatocytes.

[0047] Another group of patients are under oxidative stress or otherwisehave severe illness that makes them more susceptible than normal toacetaminophen toxicity. Such patients may include, for example, patientswith septic shock, distributive shock, hemorrhagic shock, acuterespiratory distress syndrome, organ failure, and closed head injury.Patients in this group are routinely treated with acetaminophen as ananti-pyretic and mild analgesic, which may inadvertently result insevere hepatic or renal damage.

[0048] Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range is encompassed within the invention. The upper and lowerlimits of these smaller ranges which may independently be included inthe smaller ranges is also encompassed within the invention, subject toany specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either bothof those included limits are also included in the invention.

[0049] Unless defined otherwise, all technical and scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which this invention belongs. Although any methodsand materials similar or equivalent to those described herein can alsobe used in the practice or testing of the present invention, thepreferred methods and materials are now described. All publicationsmentioned herein are incorporated herein by reference to disclose anddescribe the methods and/or materials in connection with which thepublications are cited.

[0050] It must be noted that as used herein and in the appended claims,the singular forms “a”, “and”, and “the” include plural referents unlessthe context clearly dictates otherwise. All technical and scientificterms used herein have the same meaning.

[0051] The publications discussed herein are provided solely for theirdisclosure prior to the filing date of the present application. Nothingherein is to be construed as an admission that the present invention isnot entitled to antedate such publication by virtue of prior invention.Further, the dates of publication provided may be different from theactual publication dates which may need to be independently confirmed.

EXAMPLES

[0052] The following examples are put forth so as to provide those ofordinary skill in the art with a complete disclosure and description ofhow to make and use the present invention, and are not intended to limitthe scope of what the inventors regard as their invention nor are theyintended to represent that the experiments below are all or the onlyexperiments performed. We present AZT and acetaminophen as examples ofthe model for toxicity we propose. Efforts have been made to ensureaccuracy with respect to numbers used (e.g. amounts, temperature, etc.)but some experimental errors and deviations should be accounted for.Unless indicated otherwise, parts are parts by weight, molecular weightis weight average molecular weight, temperature is in degreesCentigrade, and pressure is at or near atmospheric.

Example 1

[0053] A child or adult having a fever can be treated with a formulationcomprising 15 mg/kg acetaminophen and 1 mg/kg of either the purifiedL-enantiomer or the racemate mixture composed of equal proportions ofthe D- and L-isomers of NAC administered either serially orco-administered three or four times a day up to the highest tolerabledose, given that there will be individual variability in the ability totolerate NAC. The dose of NAC may vary from 0.03 to four times theamount of acetaminophen taken.

Example 2

[0054] A child or adult having a fever that does not respond toacetaminophen at a standard dose level can be treated with a formulationcomprising 15-50 mg/kg acetaminophen and 3-130 mg/kg of either thepurified L-enantiomer or the racemate mixture composed of equalproportions of the D- and L-isomers of NAC administered either seriallyor co-administered three or four times a day up to the highest tolerabledose, given that there will be individual variability in the ability totolerate NAC.

Example 3

[0055] A normally healthy child or adult having a low fever can betreated for several days at normal acetaminophen dosage levels with aformulation comprising 80 mg per tablet acetaminophen and 3 mg pertablet of either the purified L-enantiomer or the racemate mixturecomposed of equal proportions of the D- and L-isomers of NACadministered either serially or co-administered three or four times aday up to the highest tolerable dose, given that there will beindividual variability in the ability to tolerate NAC, the number oftablets to vary according to the patient's circumstances and bodyweight.

Example 4

[0056] A child or adult receiving nutrition parenterally can be treatedto supplement the nutrition formula with a formulation comprising 3 mgor more of either the purified L-enantiomer or the racemate mixturecomposed of equal proportions of the D- and L-isomers of NACadministered three or four times a day up to the highest tolerable dose,given that there will be individual variability in the ability totolerate NAC, variability in the amount of the cysteine source in thetotal parenteral nutrition formulation and the variability of theconcomitantly administered drugs.

Example 5

[0057] A child or adult having liver failure or liver damage or havingelevated liver enzymes and fever who is already compromised can betreated with a cold, pain, antipyretic or other formulation comprisingbetween 4 and 10 mg/kg acetaminophen and up to 130 mg/kg of either thepurified L-enantiomer or the racemate mixture composed of equalproportions of the D- and L-isomers of NAC administered either seriallyor co-administered three or four times a day up to the highest tolerabledose given that there will be individual variability in the ability totolerate NAC.

Example 6

[0058] A patient having HIV infection can be treated with a formulationcomprising a therapeutically effective amount of AZT as part of amulti-drug antiviral regimen and a toxicity-reducing amount of eitherthe purified L-enantiomer or the racemate mixture composed of equalproportions of the D- and L-isomers of NAC administered either seriallyor co-administered two, three or four times a day up to the highesttolerable dose, given that there will be individual variability in theability to tolerate NAC. It is preferred that NAC be formulated at highdoses as an effervescent tablet or in granular form in a single dosepacket to be dissolved in water to prevent untoward stomach effects.This dosage of NAC is sufficient to decrease key aspects of AZT toxicityin human HIV patients.

Example 7

[0059] AZT and NAC can be administered perinatally and neonatally toprevent vertical transmission of the HIV virus to the child. Beforedelivery, the mother is treated with a therapeutically effective amountof AZT and a toxicity-reducing amount of either the purifiedL-enantiomer or the racemate mixture composed of equal proportions ofthe D- and L-isomers of NAC administered either serially orco-administered two, three, or four times a day to the highest tolerabledose, given that there will be individual variability in the ability totolerate NAC. Dosage is continued to the child after delivery to preventoxidative stress and other AZT toxicity. It is preferred that NAC beformulated at high doses as an effervescent tablet or in granular formin a single dose packet to be dissolved in water to prevent untowardstomach effects. This dosage of NAC is sufficient to decrease keyaspects of AZT toxicity in human HIV patients.

Example 8

[0060] A patient with newly-diagnosed or suspected exposure to HIV canbe treated with a formulation comprising a therapeutically effectiveamount of AZT or other similar anti-retroviral drug as normally used anda toxicity-reducing amount of either the purified L-enantiomer or theracemate mixture composed of equal proportions of the D- and L-isomersof NAC administered either serially or co-administered two, threee orfour times a day up to the highest tolerable dose, given that there willbe individual variability in the ability to tolerate NAC. It ispreferred that NAC be formulated at high doses as an effervescent tabletor in granular form in a single dose packet to be dissolved in water toprevent untoward stomach effects. This dosage of NAC is sufficient todecrease key aspects of AZT toxicity in human HIV patients.

[0061] While the present invention has been described with reference tothe specific embodiments thereof, it should be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted without departing from the true spirit and scope of theInvention. In addition, many modifications may be made to adapt aparticular situation, material, composition of matter, process, processstep or steps, to the objective, spirit and scope of the presentinvention. All such modifications are intended to be within the scope ofthe claims appended hereto.

What is claimed is:
 1. A pharmaceutical composition useful for treatingor preventing the toxic effects of therapeutic agents in mammals,comprising a toxicity-reducing amount of N-acetylcysteine or apharmaceutically acceptable salt or derivative thereof alone or incombination with a therapeutic or greater amount of a therapeutic agent,in combination with a pharmaceutically acceptable excipient or carrier.2. A pharmaceutical composition according to claim 1 wherein each dosageunit contains at least about 1 mg N-acetylcysteine or apharmaceutically-acceptable salt or derivative thereof.
 3. Apharmaceutical composition according to claim 1, wherein the therapeuticagent is at least one antibiotic or antiviral agent.
 4. A pharmaceuticalcomposition according to claim 1 wherein the therapeutic agent is atleast one antibiotic or antiviral agent that produces oxidative stress.5. A pharmaceutical composition according to claim 1 wherein thetherapeutic agent is at least one antibiotic or antiviral agent thatproduces treatment-related decreases in subject cysteine/glutathionelevels.
 6. A pharmaceutical composition according to claim 1 wherein thetherapeutic agent is at least one analgesic, antipyretic or othertherapeutic compound.
 7. A pharmaceutical composition according to claim1, wherein the therapeutic agent is at least one analgesic, antipyreticor other therapeutic compound, wherein the compound produces oxidativestress.
 8. A pharmaceutical composition according to claim 1, whereinthe therapeutic agent is at least one analgesic, antipyretic or othertherapeutic compound, wherein the compound produces treatment-relateddecreases in subject cysteine/glutathione levels.
 9. A pharmaceuticalcomposition according to claim 6, wherein the compound is acetaminophen.10. A pharmaceutical composition according to claim 9, wherein eachdosage unit contains a standard dose of acetaminophen and at least about1 mg of N-acetylcysteine.
 11. A pharmaceutical composition according toclaim 1, wherein the therapeutic agent is an anti-retroviral agent. 12.A pharmaceutical composition according to claim 11, wherein theanti-retroviral agent is AZT.
 13. A method of treating or preventing thetoxic effects of therapeutic agents in mammals, which comprisesadministering a toxicity-reducing amount of N-acetylcysteine or apharmaceutically acceptable salt or derivative thereof, alone or incombination with a normal dosage or a greater than normal dosage of atherapeutic agent, in combination with a pharmaceutically acceptablecarrier.
 14. A method according to claim 13, wherein at least about 1 mgN-acetylcysteine or a pharmaceutically acceptable salt or derivativethereof is administered to a patient receiving nutrition parenterally.15. A method according to claim 13, wherein a therapeutic amount of atleast one antibiotic or antiviral agent is administered in combinationwith N-acetylcysteine or a pharmaceutically acceptable salt orderivative thereof.
 16. A method according to claim 13, wherein atherapeutic amount of at least one antibiotic or antiviral agent isadministered in combination with N-acetylcysteine or a pharmaceuticallyacceptable salt or derivative thereof, wherein the agent producesoxidative stress.
 17. A method according to claim 13, wherein atherapeutic amount of at least one antibiotic or antiviral agent isadministered in combination with N-acetylcysteine or a pharmaceuticallyacceptable salt or derivative thereof, wherein the agent producestreatment-related decreases in subject cysteine/glutathione levels. 18.A method according to claim 13, wherein the therapeutic agent is ananti-retroviral agent.
 19. A method according to claim 18, wherein theanti-retroviral agent is AZT.
 20. A method according to claim 19,wherein AZT is administered serially or in combination with atoxicity-reducing amount of N-acetylcysteine perinatally.
 21. A methodaccording to claim 19, wherein AZT is administered serially or incombination with a toxicity-reducing amount of N-acetylcysteineneonatally.
 22. A method according to claim 19, wherein AZT isadministered for suspected or known exposure to the HIV virus seriallyor in combination with a toxicity-reducing amount of N-acetylcysteine.23. A method according to claim 13, wherein a therapeutic amount of atleast one analgesic, antipyretic or other therapeutic compound isadministered in combination with N-acetylcysteine or a pharmaceuticallyacceptable salt or derivative thereof.
 24. A method according to claim13, wherein a therapeutic amount of at least one analgesic, antipyreticor other therapeutic compound is administered in combination withN-acetylcysteine or a pharmaceutically acceptable salt or derivativethereof, wherein the compound produces oxidative stress.
 25. A methodaccording to claim 13, wherein a therapeutic amount of at least oneanalgesic, antipyretic or other therapeutic compound is administered incombination with N-acetylcysteine or a pharmaceutically acceptable saltor derivative thereof, wherein the compound produces treatment-relateddecreases in subject cysteine/glutathione levels.
 26. A method accordingto claim 23, wherein the compound is acetaminophen.
 27. A methodaccording to claim 26, wherein the acetaminophen is administered in astandard dosage serially or in combination with at least about 1 mg perdose N-acetylcysteine to treat a fever or pain in a patient who respondsnormally to acetaminophen.
 28. A method according to claim 26, whereinthe acetaminophen is administered in a greater than standard dosageserially or in combination with at least about 4 mg/kg N-acetylcysteineto treat a fever nonresponsive to the standard dose of acetaminophen.29. A method according to claim 26, wherein the acetaminophen isadministered in a standard dosage serially or in combination with atleast about 1 mg per dose N-acetylcysteine to treat patients who requireacetaminophen during their exposure to radiation contrast agents.